NIST Researchers Holding Steady in an Atomic-Scale Tug-of-War

How hard do you have to pull on a single atom of--let's say--gold to detach it from the end of a chain of like atoms?* It's a measure of the astonishing progress in nanotechnology that questions that once would have interested only physicists or chemists are now being asked by engineers. To help with the answers, a research team at the National Institute of Standards and Technology (NIST) has built an ultra-stable instrument for tugging on chains of atoms, an instrument that can maneuver and hold the position of an atomic probe to within 5 picometers, or 0.000 000 000 5 centimeters.**

A quantum-mechanics-based simulation demonstrates how a new NIST instrument can delicately pull a chain of atoms apart. The chart records quantum jumps in conductivity as a gold contact is stretched 0.6 nanometer. The junction transitions from a 2-dimensional structure to a one-dimensional single-atom chain, with a corresponding drop in conductivity. Following the last point, at a wire length of 3.97 nm, the chain broke.

The basic experiment uses a NIST-designed instrument inspired by the scanning tunneling microscope (STM). The NIST instrument uses as a probe a fine, pure gold wire drawn out to a sharp tip. The probe is touched to a flat gold surface, causing the tip and surface atoms to bond, and gradually pulled away until a single-atom chain (see figure) is formed and then breaks. The trick is to do this with such exquisite positional control that you can tell when the last two atoms are about to separate, and hold everything steady; you can at that point measure the stiffness and electrical conductance of the single-atom chain, before breaking it to measure its strength.

The NIST team used a combination of clever design and obsessive attention to sources of error to achieve results that otherwise would require heroic efforts at vibration isolation, according to engineer Jon Pratt. A fiber-optic system mounted just next to the probe uses the same gold surface touched by the probe as one mirror in a classic optical interferometer capable of detecting changes in movement far smaller than the wavelength of light. The signal from the interferometer is used to control the gap between surface and probe. Simultaneously, a tiny electric current flowing between the surface and probe is measured to determine when the junction has narrowed to the last two atoms in contact. Because there are so few atoms involved, electronics can register, with single-atom sensitivity, the distinct jumps in conductivity as the junction between probe and surface narrows.

The new instrument can be paired with a parallel research effort at NIST to create an accurate atomic-scale force sensor—for example, a microscopic diving-board-like cantilever whose stiffness has been calibrated on NIST’s Electrostatic Force Balance. Physicist Douglas Smith says the combination should make possible the direct measurement of force between two gold atoms in a way traceable to national measurement standards. And because any two gold atoms are essentially identical, that would give other researchers a direct method of calibrating their equipment. “We’re after something that people that do this kind of measurement could use as a benchmark to calibrate their instruments without having to go to all the trouble we do, " Smith says. "What if the experiment you’re performing calibrates itself because the measurement you’re making has intrinsic values? You can make an electrical measurement that’s fairly easy and by observing conductance you can tell when you’ve gotten to this single-atom chain. Then you can make your mechanical measurements knowing what those forces should be and recalibrate your instrument accordingly.”

In addition to its application to nanoscale mechanics, say the NIST team, their system’s long-term stability at the picometer scale has promise for studying the movement of electrons in one-dimensional systems and single-molecule spectroscopy.

* The answer, calculated from atomic models, should be something under 2 nanonewtons, or less than 0.000 000 007 ounces of force.

NIST Racetrack Ion Trap is a Contender in Quantum Computing Quest

Physicists at the National Institute of Standards and Technology (NIST) have built and tested a device for trapping electrically charged atoms (ions) that potentially could process dozens of ions at once with the most versatile control of any trap demonstrated to date. The novel design is a first attempt to systematically scale up from traps that hold a few ions in a few locations to large trap arrays that can process many ions simultaneously, with the ultimate goal of building a practical quantum computer.

Photograph of NIST racetrack ion trap under development as possible hardware for a future quantum computer. The 150 zones for storing, transporting and probing ions (electrically charged atoms) are located in the center ring structure and the six channels radiating out from its edges.

If they can be built, quantum computers would rely on the curious rules of quantum mechanics to solve certain currently intractable problems, such as breaking today’s most widely used data encryption codes. The same NIST research group has previously demonstrated various components and operations of a potential quantum computer using ions as quantum bits (qubits). The trap structure is only one component, analogous to the wiring in today’s computers. Lasers are also needed to control and use the quantum data, as transistors do for classical bits today.

Made of a quartz wafer coated with gold in an oval shape roughly 2 by 4 millimeters, NIST’s “racetrack” ion trap features 150 work zones where qubits—ions encoding 1s and 0s in their “spins”—could be stored and transported using electric fields and manipulated with laser beams for information processing. The trap theoretically could be scaled up to a much larger number of zones and mass fabricated in a variety of materials. Preliminary testing of the trap, including loading of 10 magnesium ions at once and transport of an ion through a junction between channels, is described in a new paper.*

Geometry is a key feature of the new trap design. This is the first demonstration of ion transport through a junction in a trap where all electrodes are located on one flat surface, a more scalable design than the multilayer ion traps originally developed. The various electrodes are used to position and move the ions. At least three adjacent electrodes are needed to hold an ion in a dedicated energy “well.” This well and the ion can then be moved around to different locations by applying voltages to several other electrodes. The modular design would allow the addition of extra rings, which could significantly increase capabilities, according to Jason Amini, who designed the trap while a NIST postdoctoral researcher and is now at the Georgia Tech Quantum Institute in Atlanta.

“The trap design demonstrates the use of a basic component library that can be quickly assembled to form structures optimized for a particular experiment,” Amini says. “We can imagine rapid development of traps tailored to individual experiments.”

NIST scientists are continuing development of the racetrack ion trap as well as other designs. The new work was funded in part by the Intelligence Advanced Research Projects Activity and the Office of Naval Research. Four of the 10 authors of the new paper were postdoctoral or guest researchers at NIST at the time of the research and are currently affiliated with the Georgia Tech Quantum Institute, Atlanta, Ga.; Council for Scientific and Industrial Research, Pretoria, South Africa; Centre for Quantum Technologies, National University of Singapore; and Institut Neel-CNRS, Grenoble, France.

A multidisciplinary research team at the National Institute of Standards and Technology (NIST) has found* that an organic semiconductor may be a viable candidate for creating large-area electronics, such as solar cells and displays that can be sprayed onto a surface as easily as paint.

This airbrush technique deposits a well-studied material called P3HT to create spray-on transistors, which perform comparably to lab-standard equivalents made by spin coating.

While the electronics will not be ready for market anytime soon, the research team says the material they studied could overcome one of the main cost hurdles blocking the large-scale manufacture of organic thin-film transistors, the development of which also could lead to a host of devices inexpensive enough to be disposable.

Silicon is the iconic material of the electronics industry, the basic material for most microprocessors and memory chips. Silicon has proved highly successful as a substance because billions of computer elements can be crammed into a tiny area, and the manufacturing process behind these high-performance chips is well-established.

But the electronics industry for a long time has been pursuing novel organic materials to create semiconductor products—materials that perhaps could not be packed as densely as state-of-the-art silicon chips, but that would require less power, cost less and do things silicon devices cannot: bend and fold, for example. Proponents predict that organic semiconductors, once perfected, might permit the construction of low-cost solar cells and video displays that could be sprayed onto a surface just as paint is.

“At this stage, there is no established best material or manufacturing process for creating low-cost, large-area electronics,” says Calvin Chan, an electrical engineer at NIST. “What our team has done is to translate a classic material deposition method, spray painting, to a way of manufacturing cheap electronic devices.”

The team’s work showed that a commonly used organic transistor material, poly(3-hexylthiophene), or P3HT, works well as a spray-on transistor material because, like beauty, transistors aren’t very deep. When sprayed onto a flat surface, inhomogeneities give the P3HT film a rough and uneven top surface that causes problems in other applications. But because the transistor effects occur along its lower surface—where it contacts the substrate—it functions quite well.

Chan says the simplicity of spray-on electronics gives it a potential cost advantage over other manufacturing processes for organic electronics. Other candidate processes, he says, require costly equipment to function or are simply not suitable for use in high-volume manufacturing.

NIST Scientists Address 'Wrinkles' in Transparent Film Development

A closer look at a promising nanotube coating that might one day improve solar cells has turned up a few unexpected wrinkles, according to new research* conducted at the National Institute of Standards and Technology (NIST) and North Dakota State University (NDSU)—research that also may help scientists iron out a solution.

This atomic-force microscopy image shows wrinkling in a single-wall carbon nanotube membrane; the inset shows an optical reflection micrograph of the membrane without any strain. The random arrangement of the nanotubes shown in the inset creates conductivity, but wrinkling can disrupt that. Each image is 40 micrometers in width.

The scientists have found that coatings made of single-walled carbon nanotubes (SWCNTs) are not quite as deformable as hoped, implying that they are not an easy answer to problems that other materials present. Though films made of nanotubes possess many desirable properties, the team’s findings reveal some issues that might need to be addressed before the full potential of these coatings is realized.

“The irony of these nanotube coatings is that they can change when they bend,” says Erik Hobbie, now the director of the Materials and Nanotechnology program at NDSU. “Under modest strains, these films can develop irreversible changes in nanotube arrangement that reduce their conductivity. Our work is the first to suggest this, and it opens up new approaches to engineering the films in ways that minimize these effects.”

High on the wish list of the solar power industry is a cheap, flexible, transparent coating that can conduct electricity. If this combination of properties can somehow be realized in a single material, solar cells might become far less expensive, and manufacturers might be able to put them in unexpected places—such as articles of clothing. Transparent conductive coatings can be made of indium-tin oxide, but their rigidity and high cost make them less practical for widespread use.

Carbon nanotubes are one possible solution. Nanotubes, which resemble microscopic rolls of chicken wire, are inexpensive, easy to produce, and can be formed en masse into transparent conductive coatings whose weblike inner structure makes them not only strong but deformable, like paper or fabric. However, the team’s research found that some kinds of stretching cause microscopic ‘wrinkles’ in the coating that disrupt the random arrangement of the nanotubes, which is what makes the coating conduct electricity.

“You want the nanotubes to stay randomly arranged,” Hobbie says. “But when a nanotube coating wrinkles, it can lose the connected network that gives it conductivity. Instead, the nanotubes bundle irreversibly into ropelike formations.”

Hobbie says the study suggests a few ways to address the problem, however. The films might be kept thin enough so the wrinkling might be avoided in the first place, or designers could engineer a second interpenetrating polymer network that would support the nanotube network, to keep it from changing too much in response to stress. “These approaches might allow us to make coatings of nanotubes that could withstand large strains while retaining the traits we want,” Hobbie says.

Smoke Alarms + Sprinklers + Closed Doors = Lives Saved in Dorm Fires

Experimenting on a university dormitory that was scheduled to be torn down, fire researchers from the National Institute of Standards and Technology (NIST) have demonstrated that the correct combination of automatic fire sprinkler systems, smoke alarms and closed doors provided enough time and safe conditions for residents to escape safely and for firefighters to perform their job without undue hazard.

These post-fire photographs of the dorm rooms show the difference a sprinkler makes. There is little visible damage the in the top photo that had a sprinkler in the room; there was no sprinkler in the dorm room in the lower picture.

The study’s goal was to compare the hazard levels created by room fires in dormitory buildings with and without sprinklers in the room where the fire starts. Researchers used a dorm at the University of Arkansas in Fayetteville, Ark., that was scheduled to be replaced with a high-rise building.

Fires create many potentially fatal hazards, including high heat, loss of visibility and—what can be the most critical risk—toxic gases. In addition to monitoring thermal conditions and visibility, researchers also measured the oxygen, carbon monoxide and carbon dioxide levels to determine the tenability, that is, survival conditions, on the fire floor.

The five rooms used in the experiment were furnished as typical dorms are and included clothing, books and furniture. Smoke alarms were installed in the rooms and the corridors. The smoke alarms activated within 30 seconds of ignition of a trash container in a dorm room.

Experiments 1 and 2 were conducted with the dorm room door and windows closed and in both the experiments the corridor remained tenable, which would allow other students to exit safely past the room. Rooms for experiments 2 and 3 had automatic fire sprinklers installed. The automatic fire sprinklers activated within two minutes after ignition in both experiments. In the sprinklered experiments, tenability was maintained in the dorm room and the corridor.

Experiments 4 and 5 were conducted with the door of the dorm room open and no active sprinkler. In both experiments the tenability limits were exceeded in the dorm room and corridor.

The experiments also demonstrated the importance of a closed door between the fire room and corridor in limiting the spread of smoke and gasses to other areas of the building.

The studied was performed as part of the U.S. Fire Administration’s initiative to improve fire safety in college housing and in collaboration with the University of Arkansas and the Fayetteville Fire Department.

Health Information Security Conference to Run May 11-12 in D.C.

The National Institute of Standards and Technology (NIST) is co-hosting a conference to explore the current health information technology security landscape and the Health Insurance Portability and Accountability Act (HIPAA) Security Rule. The conference on “Safeguarding Health Information: Building Assurance through HIPAA Security,” presented in collaboration with the Department of Health and Human Services (HHS) Office for Civil Rights, will be held on May 11 and 12, 2010, in Washington, D.C.

This conference will provide a forum to discuss the present state of health information security, and practical strategies, tips and techniques for implementing the security requirements of HIPAA. The law promotes health care industry efficiency through the use of electronic health information while protecting the confidentiality, integrity and availability of the information. Organizations required to follow the HIPAA Security Rule include government agencies involved in health records, health care providers, health plans such as health insurance issuers and Medicaid and Medicare programs, health care clearinghouses and Medicare prescription drug card sponsors.

Plenary sessions will cover a variety of current HIPAA and health information technology topics including updates on the HHS Office of Civil Rights, administration and enforcement of the HIPAA Security Rule, risk assessments and contingency planning, logging and auditing in a healthcare context, encryption requirements and strategies in a healthcare environment, and security considerations for mobile/wireless technologies and new media in healthcare. Industry panels will discuss breach notification rules and the state of compliance with the Security Rule.

NIST provides ongoing expertise in risk management, security and standards for federal agencies and has been involved in health information technology research since 1994. NIST has responsibility through the American Recovery and Reinvestment Act of 2009 to accelerate the development and harmonization of standards and to develop conformance test tools for health information technology.

The HHS Office for Civil Rights (OCR) enforces the HIPAA Privacy Rule, which protects the privacy of individually identifiable health information; the HIPAA Security Rule, which sets national standards for the security of electronic protected health information; the confidentiality provisions of the Patient Safety Rule, which protect identifiable information being used to analyze patient safety events and improve patient safety; and the Breach Notification regulations requiring HIPAA covered entities and their business associates to notify individuals when their health information is breached.

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Three New Members Join NIST Advisory Group

Patrick Gallagher, director of the National Institute of Standards and Technology (NIST), has named three distinguished experts from industry and academia to serve on the Visiting Committee on Advanced Technology (VCAT), the agency’s primary private-sector policy advisory group. The new VCAT members—who will serve three-year terms starting on April 1—bring the body’s number to 13.

The new committee members include:

Michael McRobbie, president of Indiana University. IU’s eight-campus system has a total budget of around $2.9 billion, and more than 5,000 faculty, 11,000 staff and 100,000 students. With broad experience in fostering research partnerships, McRobbie has particular expertise in information technology, as an active researcher in computer science and logic, a co-creator of the IU School of Informatics, and the initiator of IU’s Information Technology Strategic Plan, which is considered a model for institutions across the nation.

Shaygan Kheradpir, executive vice president and chief information officer for Verizon Communications. Kheradpir is responsible for the information technology initiatives of all business units at Verizon Communications, a global company with annual revenues of more than $107 billion. An electrical engineer holding several U.S. patents, Kheradpir leads technology development and innovation for key Verizon initiatives, including having developed and implemented the systems and products for Verizon’s all-fiber network, known as FiOS.

Sujeet Chand, senior vice president and chief technology officer of Rockwell Automation. Chand is responsible for the development of technology strategy and the evolution of next-generation architecture and platforms for the company while leading R&D, standards and trade activities with a globally distributed team. Named Rockwell Engineer of the Year in 1993, Chand has led numerous innovations in industrial automation technology and applications, and holds nine patents.

The VCAT was established by Congress in 1988 to review and make recommendations on NIST’s policies, organization, budget and programs. The VCAT chair is Vinton Cerf, vice president and chief Internet evangelist for Google. VCAT’s vice chair is Alan Taub, vice president for global research and development at General Motors.

NIST Director Gallagher to Co-Chair White House Standards Committee

Whether it is to promote the development of a nationwide "Smart Grid" for electricity, optimize cyber security in federal information technology systems, or develop an effective and interoperable health IT system, technical standards play a major role, and federal agencies must work effectively with private-sector partners to ensure these efforts succeed. Toward these ends, National Institute of Standards and Technology (NIST) Director Patrick Gallagher and Department of Justice Deputy Assistant Attorney General Philip Weiser will co-chair a new Subcommittee on Standards that has been established at the White House Office of Science and Technology Policy (OSTP).

Part of the OSTP National Science and Technology Council Committee on Technology, this interagency group will provide high-level leadership so federal agencies are strategically focused and actively engaged on critical standards-related issues. In turn, the improved coordination is intended to ensure that agencies can work in a responsive and timely fashion with the private sector so that effective standards are developed and put into practice to meet national needs. The group will reinforce the ability of the federal government to work in partnership with the private sector to address the standards needed to solve national problems.

This subcommittee will also work closely with the Interagency Committee on Standards Policy (ICSP), which is chaired by Belinda Collins of NIST. The Subcommittee on Standards will provide direction and guidance to the ICSP, and will rely on the ICSP to coordinate interagency implementation of standards policy, assess progress, and develop potential policy options or guidance with the goal of removing barriers to effective standards development or use.

Good Times! Get to Know Your Radio-Controlled Clock

"How accurate is a radio-controlled clock?" National Institute of Standards and Technology (NIST) researcher Michael Lombardi asks and answers the question in a featured article of this month’s Horological Journal, published by The British Horological Institute, Limited.

Often advertised as “atomic clocks,” radio-controlled clocks get their sense of time by periodically checking the broadcast time signals from one of the world’s major time-keeping agencies, which, to be fair, are synchronized with true atomic clocks. In the continental United States, such clocks generally use the 60 kilohertz signal from NIST’s WWVB station in Fort Collins, Colo.

Lombardi explains that several factors affect the accuracy of your radio-controlled clock, including how accurate the radio station signal is, how long it takes the signal to reach your clock, how accurately your clock synchronizes with the signal, and how accurately it keeps time between synchronizations. On the whole, he says, it’s reasonable to assume that at the time of synchronization the clock is probably accurate to within not more than 30 milliseconds—plenty good enough to make an appointment on time.

NIST Advisory Committee Issues 2009 Annual Report

The Visiting Committee on Advanced Technology (VCAT) of the National Institute of Standards and Technology (NIST), the agency's primary private-sector advisory group, has sent its 2009 annual report to Congress.

The report highlights NIST’s unique and significant role in the coordination of federal development and use of documentary standards in three areas of critical national importance—Smart Grid interoperability, healthcare information technology, and cybersecurity—and expresses the Committee’s strong support for NIST to strengthen its leadership role in documentary standards affecting the nation’s priorities. It also calls for NIST to incorporate its present multi-year strategic planning process into its institutional culture, and to complete its evaluation of NIST organizational structures that could most effectively support NIST’s strategic goals and priorities.The VCAT was established by Congress in 1988 to review and make recommendations on NIST’s policies, organization, budget and programs. The 2009 report includes specific recommendations on NIST’s efforts to promote and support U.S. technological innovation and industrial competitiveness in areas such as documentary standards, planning, and research directions.